2005-2009 Honda TRX400EX/TRX400X Service Manual, Page 91Get this manual
FUEL SYSTEM three screws (whil holding the pump cover) accelerator pump cover
spring diaphragm
Visually in spect the following- diaph ragm for deterioration or pi holesspring for damagediaphragm shaft for excessive wear or damageorifice in the cover for clogging or restriction